Priority is claimed on Japanese Patent Application No. 2007-287863, filed on Nov. 5, 2007, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an inner rotor type brushless motor which has, for example, a rotor and a stator.
2. Description of the Related Art
Generally, an inner rotor type brushless motor has a stator core fitted into and fixed to a stator case, and a rotor rotatably provided with respect to the stator core, and includes permanent magnets at an outer peripheral portion thereof. This stator core includes a plurality of teeth which protrude radially inward. A coil bobbin around which a coil is wound is mounted on each of the teeth. As electric current flows into the coil, an attractive or repulsive force is generated between the rotor and the stator to rotate the rotor.
Among this type of coil bobbin, for example, there is one which is constituted by a connecting portion connecting an inner bobbin and an outer bobbin, and in which a coil is wound around the connecting portion (for example, refer to Japanese Unexamined Patent, First Application Publication No. 2004-194458). Further, an upper end of the inner bobbin is provided with a coil holding portion made of resin to which a coil starting portion of the coil is fixed, while an upper end of the outer bobbin is provided with a coil holding portion to which a winding finishing portion of the coil is fixed. After a plurality of coil bobbins is mounted on the stator core, the coil holding portion is joined to a through-hole of a substrate by soldering, and is electrically connected with lead wires drawn in from the outside.
However, in the above-mentioned brushless motor, the through-hole should be formed inside the substrate by a distance required for forming lands or patterns due to the lands or patterns being formed on the substrate. Along with this, the position of the coil holding portion to be inserted into the through-hole should be arranged more inward than necessary. That is, useless space may be created in a portion more radially outside than the through-hole, and accordingly, the wall thickness of the stator core should be made large. Thus, there is a problem in that a large winding space for the coil cannot be secured. As a result, since the occupancy of the coil decreases, an increase in loss and a decrease in motor torque may be caused. Further, in order to improve the occupancy of the coil, a motor should be made large.